Therapeutic platelet transfusion is currently estimated at 5-7 million units annually, and is expected to increase with expanded use of organ transplantation and intensive cancer chemotherapy. The health risks associated with platelet transfusion are significant primarily because of the potential for transmission of blood-home viral infectious agents despite pretransfusion blood product testing. The objective of this proposal is to develop a technique to inactivate hepatitis B virus(HBV), hepatitis non-A, non-B virus(NANBV), and cytomegalovirus(CMV) in human platelet concentrates(PC) with preservation of platelet function. Information from this project will be generally applicable to future studies of the inactivation of other viruses in blood products, to the effects of these processes on cellular and plasma components, and ultimately to the prevention of transfusion-associated viral disease. A photochemical decontamination(PCD) technique has been developed utilizing 8-methoxypsoralen (8-MOP) and long wavelength ultraviolet irradiation (UVA) to inactivate a wide spectrum of viruses in PC with preservation of in vitro platelet function. This project seeks to optimize the efficiency of the PCD technique for inactivation of extracellular and intracellular viruses in PC, to develop in vitro assays to quantify the efficiency of viral inactivation, to develop animal models for study of viral inactivation, to demonstrate the effectiveness of the PCD treatment for decontamination of PC using in vitro and in vivo assays, and to determine the in vivo survival of PCD treated platelets in primates. [1]. The photochemical inactivation kinetics of extracellular and intracellular human CN4V and murine CMV in PC using in vitro cell culture systems and a murine infectivity model will be measured. The photochemical inactivation kinetics of extracellular and intracellular duck hepadna virus(DHBV), a model for human HBV, will be determined in PC using duck hepatocyte and egg infectivity models. Feline rhinotracheitis virus(FeRTV) will be used as a model of intracellular virus, since high levels of infectivity can be achieved in PC with this agent. The effects of red cell, lymphocyte, and plasma lipid contamination on viral inactivation in PC will be determined. In addition to 8-MOP, other psoralen derivatives [4, 5', 8-trimethylpsoralen (TMP) and 4'-aminomethyl-4, 5', 8-trimethylpsoralen (AMT)] will be studied to optimize the PCD technique. [2]. The degree of intracellular photoadduct formation will be measured to assess the efficiency of proviral DNA/RNA crosslinking, and the polymerase chain reaction (PCR) amplification assay will be used to quantify the efficiency of inhibition of nuclear and viral DNA transcription. [3]. After determination of optimal inactivation conditions based on viral inactivation studies, the effects of these conditions on in vitro function of PCD treated PC will be measured. Platelet function will be assessed by measuring: platelet yield, extracellular pH, morphology score, aggregation response, secretion, extracellular lactate dehydrogenase, thromboxane B-2 production, dense body content and granule content. [4]. Human PC, to which known amounts of HBV and NANBV have been added, treated under various PCD conditions, will be transfused into chimpanzees followed by evaluation for the onset of hepatitis. [5]. The in vivo recovery, survival and hemostatic function of PCD treated cynomolgus PC will be measured in normal and thrombocytopenic cynomolgus monkeys.